Diagenetic Factors Controlling Reservoir Quality in the Faraghan Formation (Lower Permian), Darang Field, Southern Iran

Abstract

The role of diagenesis in affecting (reduction or enhancement) reservoir quality in the Faraghan Formation in Darang #1 well was investigated. The Faraghan Formation is mainly composed of sandstone facies along with minor mudstone and siltstone and grades upward into mixed carbonate –siliciclastic facies and then to Dalan Formation carbonates. Depositional environment of this formation comprises various sub-environments of a delta setting in the lower part of the formation which grades upward into a shallow marine clastic environment in the upper part. The processes enhancing reservoir quality include dissolution of carbonate grains and cements and alteration of feldspar grains. Burial history diagram shows that after deposition during Lower Permain, the formation underwent a rapid burial up to 1000 meters below sea level in Upper Permian. Then a slight uplift (about 100 meters) and gradual burial followed up to Mid-Jurassic. Afterwards the formation experienced a series of rapid and moderate uplift from Mid-Jurassic to Tertiary when the formation uplifted to around 2500 meters above sea level. The suitable conditions resulting in dissolution took place in shallow buried sandstones. These conditions occurred two times during burial history: at the early stages of eodiagenesis and during telodiagenesis. The major processes deteriorating reservoir quality include compaction and cementation. Major cement types include carbonate cements (dolomite, siderite), clay cements (kaolinite, sericite, chlorite), silica cement and pyrite cement. The most abundant cement is the carbonate cement especially dolomite. The dolomite cement occurs as intergranular and poikilotopic forms. The most frequent clay cement is sericite which dominates in sitstones and lithicarenites. Silica cement, where present, fills all the pore spaces. The least frequent cement type is pyrite which is found in two forms of poikilotopic and framboidal. Where it is found in the form of poikilotopic cement, it massively fills the pore spaces and deteriorates the porosity and permeability of the sandstones.

Reservoir Potential Assessment of the Tortonian–Calabrian Sediments from Offshore Makran (Southwest Pakistan) through a Multidisciplinary Approach

“…It is assumed that there might be a distribution of dolomite cement within the sandstone bodies, previously reported by Worden (1998) from the Triassic fluvial Chaunoy Formation, Paris Basin. The presence of dolomite cement in sandstone reservoirs is further reported by various researchers (Taylor and Gawthorpe, 2003;Sliaupa et al, 2008;Zhang and Li, 2020) and is considered to reduce reservoir porosity (Zamanzadeh et al, 2011), indeed it is assumed to be the reason for low sandstone porosity in the studied reservoir strata. Additionally, calcite cement is also reported from sandstone bodies of shallow marine environments (Walderhaug and Bjørkum, 1998;Xiong et al, 2016) and turbidite channel-fills (Marini et al, 2019).…”

Reservoir Quality Assessment of the Upper Permian Chhidru Formation, Salt and Surghar Ranges, Pakistan

“…Clay minerals can occupy different areas in a reservoir, for example, detrital, matrix in intergranular pores, pore filling by authigenic clay minerals, grain coatings, porelining rims, and as cements (Zamanzadeh et al, 2011;Baiyegunhi et al, 2017;Khan et al, 2018;Ma et al, 2018;Duan et al, 2020). The presence of clay minerals in different forms in sandstones negatively influences reservoir quality (Khan et al, 2018;Shehzad, 2019).…”

“…According to Baiyegunhi et al (2017) and Ma et al (2018), clay minerals (i.e., chlorite, illite, kaolinite, mixedlayer illite/smectite and smectite) are found as pore-lining rims, pore-filling materials and partially grain-coating in the Permian Ecca Group sandstones of South Africa and Permian Shiqianfeng sandstones of the Bohai Bay Basin of China, respectively. Clay minerals reported as cements and/or pore-filling and pore-linings and reducing the reservoir quality have also been noticed in the Permian Faraghan Formation of Iran and Ridge Sandstone of India (Zamanzadeh et al, 2011;Khan et al, 2018).…”

Tectono-sedimentary evolution of the Permian–Triassic extension event in the Zagros basin (Iran): results from analogue modelling

“…5). This formation gradually grades into the carbonates of the Dalan Formation, which indicate a shallow marine environment (Zamanzadeh et al 2000(Zamanzadeh et al , 2011. Palaeontological studies in outcrop and the entire core of the Kuhe-Surmeh anticline have been conducted on plants, and these have been interpreted to indicate a dry climate and an alluvial fan depositional environment (Ghavidel-Syooki 1988).…”